Serially connected thermochromatographic columns



F. H. BUROW Dec. 28, 1965 2 Sheets-Sheet 1 Filed June 4, 1962 R W w y ma M m 5 P l A w 1 a T m 4 P F Y R @w B W *EkumkwQ N.% %k WPQQAQNWQ mm ww M w 5 F. H. BUROW 3,225,521

SERIALLY CONNECTED THERMOCHROMATOGRAPHIC COLUMNS Dec. 28, 1965 2Sheets-Sheet 2 Filed June 4, 1962 All WBEMQQQQSQU WmKBEQQ WEE IN V ENTOR. B/{fP/INA H BZ/AOW ML United States Patent 0 OMA- This inventionrelates to a chromatographic separation method and apparatus and moreparticularly to a method and apparatus of such kind involving separatetemperature programming for a plurality of serially connectedchromatographic separating zones.

In the characterization of broad boiling range mixtures, e.g., gasolineand naphtha, it is frequently desired to separate the lower boilingcomponents, for which detailed chromatographic calibration informationis available, from the higher boiling components, for which no suchinformation is available. In this way the lower boiling components canbe subjected to detailed chromatographic analysis, and the higherboiling components can be subjected to some other form of detailedanalysis, for example, mass spectrometry, infrared spectrometry,chemical analysis, or the like. It is very important that the separation of lower-boiling and higher-boiling components be precise, asthe detailed analysis of the separated groups of components iscomplicated by overlapping of components in the separated componentgroups. Thus, the detailed chromatographic analysis of a C or lightergasoline fraction may require several times as much operating time whena small amount of C material is present than when C is the highestboiling component of the fraction, and the situation is worsened stillby the presence of even higher-boiling components. As only the C andlighter fraction can be resolved into individual components, a completequantitative analysis of this fraction cannot be obtained if part of a Ccomponent remains in the heavier fraction where it cannot bequantitatively determined.

Fractional distillation, even in highly developed form, is impracticalfor sharp separations of the kind required for the purpose indicated,because of the closeness of the boiling points involved and because ofthe presence of reflux liquid in the fractionating column. Toillustrate, the careful fractionation of a naphtha sample in a highlyefiicient laboratory fractional distillation column nine feet in lengthand one inch in diameter, and having the equivalent of 200 theoreticalplates, required a period of 405 hours to complete, and more than 100differently boiling cuts were obtained. Even so, much overlappingoccurred; for example, approximately 30 of the cuts were found to tocontain C hydrocarbons.

While sharp separations of the kind desired can be obtained by gaschromatography using very small samples, difficulties are encounteredwhen samples are utilized of a size sufficient for further operations(e.g., chemical analysis) which require relatively large quantities.This is because larger diameter columns and greater carrier gas flowrates ordinarily are required with larger samples in order to obtain thedesired resolution. However, such greater carrier gas flow ratesinterfere with the collection and recovery of the separated components,as the components have to be condensed out of the hot carrier gas. Theincreased velocity and quantity of the hot carrier gas hinder thecomplete condensation and recovery of the components.

The present invention relates to a chromatographic method and apparatusfor separating a difiicultly separable, wide-boiling range mixturecontaining a plurality of close-boiling components in an amountsufficient to permit physical recovery of separated portions of a sizesufficient for further analysis, into at least two sharply definedportions containing different components, With essentially completerecovery of sample. Broadly, in accordance with the method of thisinvention, a partial separation of lighter components from heaviercomponents of the mixture is effected in a first chromatographicseparating zone by introducing into said zone a stream of carrier gasand a vaporous sample of said mixture of a size sufiicient to permitphysical recovery of separate portions in an amount sufiicient forfurther analysis. The partly separated components are removed from thechromatographic separating zone in the order of separation by continuingthe flow of carrier gas therethrough, with complete removal of theheavier components being effected by gradually increasing thetemperature of the chromatographic separating zone to a temperaturesufficient to insure elution of these components. A further separationof the partly separated components of the mixture is effected byintroducing the efiluent from the first zone into a secondchromatographic separating zone, said second zone being at a lowertemperature than said first zone during at least a substantial part ofthe time in which the temperature of the first zone is being increased.The further separated components of the mixture are removed in the orderof separation from the second chromatographic separating zone byoontinuing the flow of carrier gas therethrough, and complete removal ofthe heavier components is effected by gradually increasing thetemperature of the second zone to a temperature sufficient to insureelution of such components. Separated components are separatelyrecovered as desired from the effluent carrier gas.

The apparatus of the present invention involves as its essentialsubcombination, a carrier gas source, a plurality of serially connectedchromatographic separating zones, means defining a path of flow for saidcarrier gas connecting said carrier gas source and the firstchromatographic separating zone in said series, said means beingprovided with means permitting introduction of a sample of a fluidmixture to be separated into the path of fiow of said carrier gas,detecting means for sensing changes in the composition of the efiiuentfrom at least one of said zones, and separately controllable heatingmeans for gradually raising the temperature of each of saidchromatographic separating zones. The invention also includescombinations including the above-indicated apparatus wherein the meansdefining a path of flow for the carrier gas is also provided with meansfor preheating the carrier gas prior to introduction thereof into thefirst chromatographic separating zone, and with means for heating thefluid mixture sample within the path of flow of said carrier gas. Thepresent invention also includes combinations of the above-indicatedapparatus including means for separately recovering separated componentsfrom the eflluent carrier gas.

Referring briefly to the drawings, FIGURE 1 is a diagrammaticrepresentation of one suitable analytical instrument structure in whichthe method of this invention can be carried out. FIGURES 2A and 2Btogether comprise a reproduction of a fragment of a recording chart ofthe type obtainable by the apparatus of FIGURE 1, showing a portion of achromatogram, that is, a plot of the differential change in detectorsignal strength with elapsed time, for a gasoline sample separated inaccordance with the present invention.

The present invention can be more readily understood with detailedreference to FIGURE 1, Thus, numeral 2 in FIGURE 1 designates a carriergas source, which may conveniently comprise a cylinder containingliquefied helium gas. It will be understood that other suitable eluentfluids can be employed as the carrier gas. In every instance, thecarrier gas should be a material that is less strongly held by thestationary phase in the chromatographic separating column than any ofthe components of the fluid mixture that is to be subjected to analysis.Helium is especially advantageous as a carrier gas when a detectorutilizing the principal of thermal conductivity is employed, as this gashas a thermal conductivity considerably higher than any of thecomponents of the particular fluid mixtures disclosed herein, but othergases can be employed. Examples of other carrier gases can be employed.Examples of other carrier gases are argon and nitrogen.

Numeral 4 in FIGURE 1 indicates the gas cylinder pressure regulator andvalve, and numeral 8 represents a flow controller for establishing aconstant rate of flow of carrier gas into and through the system.Numerals 6 and 10 comprise conduits connecting the carrier gas cylinder2 with a carrier gas preheater 12.

Preheater 12 comprises means for preheating the carrier gas prior toadmixture thereof with the sample to be analyzed, and includes a highsurface area, corrosion resistant packing 14 having good thermalconductivity characteristics, resistance heating windings 116, and avariable resistance 18 for controlling the electrical current input andthus the heat output of resistance windings 16. Stainless steel turningsin the form of loose spirals and having a diameter in the range ofperhaps 0.05 to 0.1 cm. are suitable packing material for purposes ofthis invention, but other packing materials in other forms can be used.For example, there can be used commercial wire spring distillationcolumn packings marketed under the names of Heli-Pac, Double SpiralPodbielniak Distillation Column Packing, Fenske Spirals, and the like.Preheating of the carrier gas is desirable in order to assist invaporization of the vaporizable components of the sample to be analyzedand also to establish a temperature gradient at least in the firstchromatographic separating zone in the series. This temperature gradientis effected by transfer of heat from the carrier gas to the columnpacking.

The temperature at which the preheater is operated can be anytemperature that will insure complete vaporization of the components ofthe mixture to be analyzed that are desired to be vaporized and thatwill not cause decomposition of the mixture components. It is preferredthat the temperature employed in the preheater be somewhat greater, forexample, to C. greater, than the temperature employed in the flashchamber 20 downstream of the carrier gas preheater. This temperaturedifference compensates for the temperature drop that occurs withvaporization of sample components in flash chamber 20.

The outlet of the carrier gas preheater is connected by a conduit 19 tothe inlet of a tubular flash chamber 20 which constitutes means forvaporizing at least a portion of the fluid mixture samples to besubjected to analysis. Like carrier gas preheater 12, flash chamber 20is provided with a high surface area packing 22 having good thermalconductivity characteristics, and with resistance heating windings 24whose heat output is controlled by a variable resistance or rheostat 28.Packed flash chamber structure of a kind suitable for the purposes ofthis invention is described in further detail and claimed in copendingpatent application Serial No. 199,882, filed June 4, 1962, in the nameof Frank H. Burow. Flash chamber 20 is also provided with access means26 permitting introduction of sample at or near its inlet end. Means 26simply comprises a housing adapted to maintain a puncturable siliconerubber diaphragm 27 in gas-tight contact with the surface of tubularflash chamber 20 in the immediate vicinity of an aperture thereinproviding access to the interior of chamber 20. Means 26 is providedwith a vertical passageway, indicated by dotted lines, permitting accessto rubber diaphragm 27 by conventional sample-introducing means, notshown.

The temperature at which the flash chamber is maintained will dependupon the nature of the mixture subjected to analysis. Any temperaturecan be used that is suflicient to insure full vaporization of theheaviest or highest boiling portions of the mixture that are to bevaporized, but insuflicient to decompose any of the components of themixture. For reasonably rapid vaporization, the temperature to which theflash chamber is heated will be in the range of about the 50 percent andthe percent distillation points for the volatilizable portion of themixture. Thus, ASTM D910 specifications for high volatile aviationgasoline provide for a maximum 50 percent distillation point of 221 F.C.) and ASTM D439 specifications for low volatile motor gasoline providefor a maximum 90 percent distillation point of 392 F. (200 0).Accordingly, for separation of gasoline or naphtha samples, atemperature in the range of about 105 to 200 C. is suitable. Atemperature that does not unduly shorten the life of the rubber disc 27is preferred. In this respect, temperatures in the neighborhood of about-l65 C. have been found suitable for the analysis of hydrocarbonmixtures boiling in the gasoline and naphtha range.

Numerals 32, 34, 36, and 38 comprise serially connected chromatographicseparating zones or columns, the inlet of column 32, the first in theseries, being connected to the outlet of flash chamber 20 by means ofconduit 30. Separating columns 32, 34, 36, and 38 are serially connectedby means of conduits 48, 50, and 52. Columns 32, 34, 36, and 38 areprovided, respectively, with resistance heating windings 40, 42, 44, and46 whose heat outputs are controlled, respectively, by rheostats 58, 60,62, and 64. The maximum temperature to which col umns 32, 34, 36, and 38are heated will be governed by the same considerations controlling theselection of the temperature employed for flash chamber 20. Columns 32,34-, 36, and 38 are further provided with thermal insulation material54, and with housing 56 therefor, to minimize heat transfer to theambient atmosphere and between adjacent columns.

In a preferred embodiment columns 32, 34, 36, and 38 are partitioncolumns and are packed with particles of an inert porous solid providedwith a coating of a liquid or semi-liquid material suitable for theparticular fluid mixture undergoing separation. Celite-type kieselguhrand insulating brick made from the same material of a particle sizebetween about 30 and 100 mesh, preferably between about 30 and 60 mesh,are examples of suitable inert supporting materials for use in packedpartition columns. Partition columns are also known in which the innerwall of the column comprises the solid support, as is the case ininstances of coated capillary chromatographic columns. A wide variety ofliquid materials can be used as the stationary phase material inchromatographic partition columns. When the columns are subjected toelevated temperatures, as disclosed herein, liquid materials of lowvolatility (high boiling point) are preferred as the stationary phasematerial. An example of a liquid or semi-liquid material suitable foruse in partition columns useful in the present invention for separationat temperatures below about 250 C. is silicone gum or rubber. Othersuitable materials are silicone oils such as General Electric CompanySF96 (1000) silicone oil,

which is useful at temperatures in the range of 0 C. to 250 C., andsilicone gums such as General Electric Company SE3O silicone gum, whichis useful at temperatures as high as 300 C. Still other examples arepolyethylene, squalane, and paraflin wax. Although partition columns arepreferred for the separation of hydrocarbon mixtures such as gasoline,naphtha and the like, it will be understood that insofar as theprinciples of the invention are concerned, the chromatographicseparating columns employed can be adsorption columns. In suchinstances, separation of mixtures occurs as a result of differentialadsorption of the components of the mixture subjected to analysis on thesurfaces of an inert, porous adsorptive solid employed as the columnpacking. Examples of suitable adsorption column packings includedia-tomaceous earth, silica gel, and activated charcoal, each having abulk density less than 0.4 gram per ml. and a particle size in the rangementioned above.

Numeral 66 constitutes means for heating the effluent from the lastchromatographic separating column 38 in the series so as to assure anessentially constant temperature at the inlet of the detector '78. Means65 should be maintained at a temperature suificient to preventcondensation of the separated components, but not so great as to promotethermal decomposition. Heating means 66, similarly as preheater 12 andflash heater 29 is provided with a corrosion resistant, high surfacearea packing 6% of good thermal conductivity characteristics, and withresistance heating windings 7% whose heat output is controlled byrheostat 72. Numerals 74 and 76 denote, respectively, conduitsconnecting the outlet of column 38 with the inlet of heater 66 and theoutlet of heater 66 with the inlet of detector '78.

Detector 78 comprises means for sensing changes in the composition ofthe effluent from column 38, for example, a thermal conductivity celldetector. Detecting means 78 is provided with heating means, not shown,to maintain the detector at a constant temperature, which should besufficient to avoid condensation of the separated components. Anysuitable detecting device can be used that is capable of utilizing someproperty of the detected component to create a signal, usually anelectrical current, proportional to the concentration of that componentin the effluent. Good results are obtainable by the use of conventionalthermal conductivity detecting cells, as in the illustrated embodiment,but other detectors responsive to changes in the composition of theeffluent gas, including gas density balances, radiological ionizationdetectors and flame temperature detectors can be used. Of course, if adetector that is destructive to the detected components is employed, theeffluent stream of separated components should be split, with one branchbeing directed to the detector and the other to suitable collectingmeans. Numeral 8i) denotes recording means associated with detector 78for indicating the differential variation in effluent composition withtime, detected by means 78. Recorder 80 functions simply by convertingthe electrical output of detector 78 to mechanical motion in the form ofa recording pen drive means, and by causing the recording pen to moverelative to the surface of a recording chart that advances with apredetermined rate.

Numeral 82 denotes conduit means connecting the outlet of detector 78with means for separately recovering components separated in thechromatographic separating columns. The recovery means comprises atwo-way valve means 84 and condenser traps 86 and 83 (shown here insimplified form), insulating vessel 90 and a cooling source 92 such asDry Ice.

In operation of the apparatus illustrated in FIGURE 1, rheostats 18, 28and 72 are set to provide the desired heat output in resistance windings16, 24, and 79, respectively, and valves 4 and 8 are set to provide aconstant carrier gas flow at the desired rate through the system. Aftercarrier gas preheater 12 and flash chamber 20 have reached the desiredtemperature as indicated by thermocouples, not shown, attached thereto,a sample of a fluid mixture to be separated, for example, gasoline,having a size of about 2.5 ml. is introduced into the inlet end of flashchamber 20 through means 26 by the use of a hypodermic needle, notshown. The gasoline components are vaporized by contact with pre-heatedpacking 22 and by contact with the preheated carrier gas. The vaporizedcomponents are swept through flash chamber 20 by means of the stream ofcarrier gas. A rough separation of the sample is eflected at the outsetin flash chamber 20 as a result of the tortuous passageways provided bythe flash chamber packing 22 and as a result of the dilferentialdiffusivity of the various components of the mixture to be separated.The partially separated sample is caused to flow into chromatographicseparating column 32 by means of the constant flow of carrier gas.

A downward temperature gradient in the direction of flow will exist atleast in column 32 by virtue of the transfer of heat from the preheatedcarrier gas to the column packing during passage therethrough, andpossibly in one or more subsequent columns. Establishment of atemperature gradient in the first chromatographic separating zonecontacted by the sample is important. Such gradient permits the largesize sample employed to be sufliciently spread out along the length ofthe small diameter analytical column that the column packing can stillbe effective to exert a partitioning eflect on the components of thesample and will not become choked with the large volume of the sample.In other words, if the sample is not somewhat spread out along thelength of the small diameter analytical column, there will not be enoughpacking surface available to contact the sample and elfect apartitioning of the components, and a much greater column length will berequired to eifect the same degree of separation that is obtained by ashorter length of column when the sample is initially distributed over arelatively longer portion. The temperature gradient functions todistribute the sample over a relatively large portion of the column byvirtue of the fact that the gradual drop in temperature encountered bythe sample components as they advance through the column slows the rateof advance of the heavier components much more greatly than the lightercomponents. In this manner choking of the column by the relatively largesample is avoided.

Having avoided choking of the column with the sample, it might now bepossible to effect the desired resolution of the sample simply bycontinuing to pass the carrier gas through a chromatographic separatingzone until all of the products were eluted, provided that a column ofsufiicient length were provided in the first instance. However, in theinstance of a wide boiling range mixture containing close boilingcomponents, the column length, and consequently, the elution time,required for such resolution would be prohibitively great. In order toeffect the desired degree of resolution in a relatively short lengthchromatographic separating column, a further downward temperaturegradient in the direction of flow, in addition to that resulting fromthe preheated carrier gas, is set up between chromatographic separatingcolumn 32, the first in the series, and chromatographic separatingcolumn 38, the last in the series. This temperature gradient is broughtabout by switching on variable rheostats 58, 60, 62, and 64 insequential order. As a result of the sequential commencement of heatingin the chromatographic separating zones, the temperature of eachsuccessive zone in the series will be lower than that of its precedingzone during a substantial part of the time in which the temperature ofthe preceding zone is being increased. When optimum heating rates areutilized, the temperature of each successive chromatographic separatingzone in the series will be lower than that of the preceding zone whenelution from such preceding zone is complete.

As the partly separated components move through the serially connectedchromatographic separating zones, :they progress step-wise fromrelatively warmer to relatively cooler zones, where the temperaturereduction tends to spread out the sample still more widely by virtue ofa greater slowing effect on the relatively heavier components of thesample. On the other hand, the elution time for the heaviest componentsis not greatly increased by the downward temperature gradient as thetemperature in each of columns 32, 34, 36, and 38 gradually increases tothe limit permitted by the rheostat settings employed. Thus, by theestablishment of a downward temperature gradient along the lengths ofthe chromatographic separating zones, an unusual degree of sampleresolution is obtained per unit column length, whereby large sizesamples can be effectively resolved in a short time, and an increase inelution time for the heaviest components of the mixture is avoided byimposing a gradually rising temperature on each of the chromatographicseparating zones in sequence.

The separated components pass out of the chromatographic separating zonethrough line 74 into heater 66, where their temperature is raised to thedegree desired prior to detection in detector '78. The variations in theeffluent composition are detected in thermal conductivity cell 78 andrecorded by recorder 80. The separated components are recovered from theeffluent carrier gas by condensation and trapping out in refrigeratedtrap 86. When the desired cut point is reached as indicated by recorder80, two-way valve 84 is switched and the subsequently eluted componentsare recovered from the efiiuent carrier gas by condensation and trappingin refrigerated trap 88.

Light ends, contained in trap 86, can then be subjected to detailedanalysis, for example, by chromatographic analysis in a capillarycolumn, and the heavier ends, contained in trap 88, can be subjected todetailed analysis by infrared spectrometry, mass spectrometry, or thelike.

In a specific embodiment, the carrier gas preheater and the flashchamber were constructed, respectively, of eightinch and 14-inch lengthsof Az-inch standard stainless steel pipe having an inside diameter ofapproximately /8- inch. Each of these chambers was packed loosely withstainless steel spirals of the kind described in a density correspondingto about 0.8 gram of packing per inch of pipe length. Both chambers werewound with a total of about 30 feet of ZO-gauge (B and S)asbestos-covered, Nichrome wire that had been threaded into a glassfabric insulating sleeve. All variable resistances were 7.5 ampereVariac rheostats having a graduated output voltage from 0 to 140. Eachof the chromatographic separating columns was formed from four feet of%-11'1Ch standard stainless steel pipe having an inside diameter ofabout 7 -inch. Each column was wound with 30 feet of Nichrome resistancewire of the kind indicated above and insulated as described. The columnswere packed with Johns Manville C-22 Silocel crushed firebrick having asize of 30, +60 mesh, and having deposited thereon a silicone rubbergum, General Electric SE-30, in the amount of 20 percent by weight. Thecolumns were connected in series by lengths of A-inch stainless steeltubing, unpacked.

In starting up the apparatus the output voltage of the preheater Variacwas set at 24 which corresponded to a preheater temperature of 184 C.,and the output voltage of the flash chamber Variac was set at 39, whichcorresponded to a flash chamber temperature of about 164 C. The outputvoltage of the effluent heater Variac was set at 22, which correspondedto a heater temperature of about 182 C., and the output voltage of thedetector heater Variac, not shown, was set at 76, which corresponded toa detector temperature of about 220 C. The thermal conductivity cellfilament current was 110 milliamperes, and a 100 millivolt recorder wasconnected to the thermal conductivity detector. A helium carrier gasflow of 100 cc. per minute was passed through the system.

o 0 After the system reached the desired starting temperatures, a 2.4cc. sample of a 400 F. end point gasoline was introduced into the flashchamber. The temperature programs of the chromatographic separatingcolumns, expressed in Variac output voltage settings, was as indicatedin the following table:

At the end of the separation all of the chromatographic separatingcolumns were at a temperature of about to C.

When all of the C components had cleared the detector as indicated onthe recording chart of the recorder (see the cut point marked on FIGURE2A and FIGURE 23) the flow of efiluent was switched to a secondcondenser trap, and C and heavier components were recovered from theefiiuent carrier gas therein. The recovered fractions equalled 96.88percent of the amount of the sample. The C and lighter components andthe C and heavier components were then separately subjected to detailedanalysis by appropriate methods.

The herein-disclosed invention is not limited to separation of thelighter and heavier components in gasoline or to any particularoperating conditions, as it also can be used to separate large-sizesamples of other wide boiling range mixtures containing close boilingcomponents into two or more sharply defined groups of components. Forexample, the herein-disclosed invention can be used to separate naphtha,jet fuel, and the like into the respective component groups containedtherein for further detailed analysis by appropriate methods. Althoughthe herein-disclosed invention is particularly adapted for separation oflarge-size samples, with physical recovery of separated components, theapparatus nevertheless can be used merely for analytical separation ofconventional, small-size samples, with remarkably good resolutionconsidering the relatively short column length. It will also beappreciated that while the herein-disclosed instrument has particularadvantages when the rising temperature program is initiated in eachsucceeding chromatographic separating zone at a time later than that ofthe preceding zone, it will be appreciated that the instrument isnevertheless flexible, in that the temperature programs for each of theseparating zones also can be simultaneously initiated, whereupon theseparate zones will function as a single chromatographic separatingcolumn having a single rising temperature program. In addition, whilethe illustrated embodiment is adapted for manual sample introduction andmanual initiation of temperature programs, it will be appreciated thatthe instrument can be partly or fully automated by the use ofconventional automatic sample injection means, sequence controllers andthe like. Although the embodiment illustrated utilizes four separateseparating columns, it will be understood that the separate zones cancomprise successive portions of a single column. It will also beappreciated that the invention is not limited to any particular numberof separating zones beyond two. Greater resolution will be obtained,however, with increasing numbers of separately temperature-programmedseparating zones.

Numerous modifications and alternative embodiments of the invention asdisclosed herein will readily suggest themselves to those skilled in theart. Accordingly, the scope of the invention is not to be limited by theembodiments disclosed herein but only by the scope of the claimsappended hereto.

I claim:

1. A chromatographic method for separating a wide boiling range mixturecontaining a plurality of close-boil ing components, comprisingeffecting a partial separation of lighter components from heaviercomponents of the mixture at a relatively low temperature of thetemperature program in a first elongated, temperature-programmedchromatographic separating column by introducing into said column aflowing stream of preheated carrier gas and a vaporous sample of themixture to be separated, removing partly separated components from saidfirst chromatographic separating column in the order of separation bycontinuing the flow of carrier gas therethrough and effecting a furtherseparation of the partly separated components and accelerating elutionof the partly separated components from said first chromatographicseparating column by gradually increasing the temperature of the entirefirst chromatographic separating column uniformly over its entirelength, thereafter effecting complete removal of the heavier componentsby further gradually increasing the temperature of said firstchromatographic separating column to a temperature suflicient to insureelution of said heavier components from said first chrornatographicseparating column, efiecting a further separation of the partlyseparated components of the mixture by passing the entire effluent fromthe first column into a separate, second elongated,temperature-programmed chromatographic separating column spaced apartfrom and fluidly communicating with said first column, said secondchromatographic column being at a lower temper ature then said firstchromatographic column during at least a substantial part of the time inwhich the temperature of said first column is being increased, removingthe further separated components of the mixture in the order ofseparation from the second chromatographic separating column andaccelerating elution of the further separated components in that form,by continuing the flow of carrier gas therethrough and effecting a stillfurther separation of the components and accelerating elution of thethusseparated components from said second chromatographic separatingcolumn by gradually increasing the temperature of the entire secondchromatographic column uniformly over its entire length, and thereafteretfecting com plete removal of the heavier components from said secondchromatographic column by further gradually increasing the temperatureof said second column to a temperature sufficient to insure elution ofsaid heavier com ponents.

2. A chromatographic method for separating a normally liquid, wideboiling range mixture containing a plurality of close-boiling componentsinto at least two portions of different composition, comprisingestablishing a temporary temperature gradient in a first elongated,temperature-programmed chromatographic separating column by establishinga flow therethrough from a preceding sample vaporizing zone of apreheated carrier gas, introducing into said sample vaporizing zone aliquid sample of said mixture of a size suificient to permit physicalrecovery of said portions, effecting a partial separation of the samplemixture by vaporizing the components of the mixture that are vaporizableat the conditions of the system by passage therethrough of saidpreheated carrier gas, said carrier gas being preheated to a temperaturesufficient to assist in vaporizing the vaporizable components of themixture to be separated, effecting a further partial separation oflighter components from heavier components of the mixture at arelatively low temperature of the temperature program in said firstcolumn by introducing into said column a flowing stream of the preheatedcarrier gas and the vaporized sample of the mixture, re moving partlyseparated components from said first chromatographic separating columnin the order of separation by continuing the flow of carrier gastherethrough and effecting a further separation of the partly separatedcomponents and accelerating elution of the partly separated componentsfrom said first chromatographic separating column by graduallyincreasing the temperature of the entire first chromatographicseparating column uniformly over its entire length, thereafter effectingcomplete removal of the heavier components by further graduallyincreasing the temperature of said first chromatographic separatingcolumn to a temperature sufiicient to insure elution of said heaviercomponents from said first chromatographic separating column, effectinga further separation of the partly separatted components of the mixtureby passing the entire eflluent from the first column into a separate,second elongated, temperature-pragrammed chromatographic separatingcolumn spaced apart from and fluidly communicating with said firstcolumn, said second chromatographic column being at a lower temperaturethan said first chromatographic column during at least a substantialpart of the time in which the temperature of said first column is beingincreased, removing the further separated components of the mixture inthe order of separation from the second chromatographic separatingcolumn and accelerating elution of the further separated components inthat form, by continuing the flow of carrier gas therethrough andeffecting a still further separation of the components and acceleratingelution of the thus-separated components from said secondchromatographic separating column by gradually increasing thetemperature of the entire second chromatographic column uniformly overits entire length, and thereafter effecting complete removal of theheavier components from said second chromatographic column by furthergradually increasing the temperature of said second column to atemperature sufiicient to insure elution of said heavier components.

3. A chromatographic separating apparatus comprising a carrier gassource, a plurality of serially connected, spaced-apart, separate,elongated chromatographic separating columns, each such column having aninlet and an outlet, means defining a path of carrier gas fiow betweenthe inlet of each successive chromatographic separating column in theseries and the outlet of the next preceding chromatographic separatingcolumn in the series, conduit means defining a path of carrier gas flowconnecting said carrier gas source and the inlet of the firstchromatographic separating column of the series, means associated withsaid conduit means for permitting introduction of a sample of a fluidmixture to be separated into the path of flow of said carrier gas,detecting means operatively connected with said chromatographicseparating apparatus for sensing changes in the composition of theeflluent carrier gas from the chromatographic separating columnpreceding the detecting means, separately controllable heating means forsuccessively and at intervals gradually raising the temperature of eachentire chromatographic separating column uniformly along its entirelength, in the order in which it appears in the series, said heatingmeans being constructed and arranged so that a successive column neverreaches any temperature above its starting temperature before the sametemperature has been reached by the preceding column.

4. A chromatographic separating apparatus comprising a carrier gassource, a plurality of serially connected, spaced-apart, separate,elongated chromatographic separating columns, each such column having aninlet and an outlet, means defining a path of carrier gas fiow betweenthe inlet of each successive chromatographic separating column in theseries and the outlet of the next preceding chromatographic separatingcolumn in the series, conduit means defining a path of carrier gas flowconnecting said carrier gas source and the inlet of the firstchromatographic separating column in the series, said conduit meansbeing provided with means for heating the carrier gas and with meanspermitting introduction of a sample of the mixture to be separated intothe path of flow of the heated carrier gas, detecting means operativelyconnected with said chromatographic separating apparatus for sensingchanges in the composition of the effiuent carrier gas from thechromatographic separating column preceding the detecting -means,separately controllable heating means for successively and at intervalsgradually raising the temperature of each entire chromatographicseparating column uniformly along its entire length, in the order inwhich it appears in the series, said heating means being constructed andarranged so that a successive column never reaches any temperature aboveits starting temperature before the same temperature has been reached bythe preceding column, and means connected to the outlet of the lastchromatographic separating column in the series and positioneddownstream of said detecting means, for separately recovering separatedcomponents of the mixture from the eflluent carrier gas obtained fromthe last chromatographic separating column in the series.

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REUBEN FRIEDMAN, Primary Examiner.

1. A CHROMATOGRAPHIC METHOD FOR SEPARATING A WIDE BOILING RANGE MIXTURECONTAINING A PLURALITY OF CLOSE-BOILING COMPONENTS, COMPRISING EFFECTINGA PARTIAL SEPARATION OF LIGHTER COMPONENTS FROM HEAVIER COMPONENTS OFTHE MIXTURE AT A RELATIVELY LOW TEMPERATURE OF THE TEMPERATURE PROGRAMIN A FIRST ELONGATED, TEMPERATURE-PROGRAMMED CHROMATOGRAPHIC SEPARATINGCOLUMN BY INTRODUCING INTO SAID COLUMN A FLOWING STREAM OF PREHEATEDCARRIER GAS AND A VAPOROUS SAMPLE OF THE MIXTURE TO BE SEPARATED,REMOVING PARTLY SEPARATED COMPONENTS FROM SAID FIRST CHROMATOGRAPHICSEPARATING COLUMN IN THE ORDER OF SEPARATION BY CONTINUING THE FLOW OFCARRIER GAS THERETHROUGH AND EFFECTING A FURTHER SEPARATION OF THEPARTLY SEPARATED COMPONENTS AND ACCELERATING ELUTION OF THE PARTLYSEPARATED COMPONENTS FROM SAID FIRST CHROMATOGRAPHIC SEPARATING COLUMNBY GRADUALLY INCREASING THE TEMPERATURE OF TNE ENTIRE FIRSTCHROMATOGRAPHIC SEPARATING COLUMN UNIFORMLY OVER ITS ENTIRE LENGTH,THEREAFTER EFFECTING COMPLETE REMOVAL OF THE HEAVIER COMPONENTS BYFURTHER GRADUALLY INCREASING THE TEMPERATURE OF SAID FIRSTCHROMATOGRAPHIC SEPARATING COLUMN TO A TEMPERATURE SUFFICIENT TO INSUREELUTION OF SAID HEAVIER COMPONENTS FROM SAID FIRST CHROMATOGRAPHICSEPARATING COLUMN, EFFECTING A FURTHER SEPARATION OF THE PARTLYSEPARATED COMPONENTS OF THE MIXTURE BY PASSING THE ENTIRE EFFLUENT FROMTHE FIRST COLUMN INTO A SEPARATE, SECOND ELONGATED,TEMPERATURE-PROGRAMMED CHROMATOGRAPHIC SEPARATING COLUMN SPACED APARTFROM AND FLUIDLY COMMUNICATING WITH SAID FIRST COLUMN, SAID SECONDCHROMATOGRAPHIC COLUMN BEING AT A LOWER TEMPERATURE THEN SAID FIRSTCHROMATOGRAPHIC COLUMN DURING AT LEAST A SUBSTANTIAL PART OF THE TIME INWHICH THE TEMPERATURE OF SAID FIRST COLUMN IS BEING INCREASED, REMOVINGTHE FURTHER SEPARATED COMPONENTS OF THE MIXTURE IN THE ORDER OFSEPARATION FROM THE SECOND CHROMATOGRAPHIC SEPARATING COLUMN ANDACCELERATING ELUTION OF THE FURTHER SEPARATED COMPONENTS IN THAT FORM,BY CONTINUING THE FLOW OF CARRIER GAS THERETHROUGH AND EFFECTING A STILLFURTHER SEPARATION OF THE COMPONENTS AND ACCELERATING ELUTION OF THETHUSSEPARATED COMPONENTS FROM SAID SECOND CHROMATOGRAPHIC SEPARATINGCOLUMN BY GRADUALLY INCREASING THE TEMPERATURE OF THE ENTIRE SECONDCHROMATOGRAPHIC COLUMN UNIFORMLY OVER ITS ENTIRE LENGTH, AND THEREAFTEREFFECTING COMPLETE REMOVAL OF THE HEAVIER COMPONENTS FROM SAID SECONDCHROMATOGRAPHIC COLUMN BY FURTHER GRADUALLY INCREASING THE TEMPERATUREOF SAID SECOND COLUMN TO A TEMPERATURE SUFFICIENT TO INSURE ELUTION OFSAID HEAVIER COMPONENTS.